In general, a hybrid vehicle or an electric vehicle, called an eco-friendly vehicle, may generate driving power with an electric motor (hereinafter called “drive motor”), which obtains torque from electrical energy.
The drive motor includes a stator and a rotor. The stator is disposed in a motor housing, and the rotor is disposed at a predetermined air gap therefrom at the inside of the stator. The stator includes a stator core made of an electric steel plate and a coil wound around the stator core.
A large amount of heat is generated according to a current applied to the coil. Accordingly, in order to prevent damage to the drive motor due to the heat and to continuously ensure stable operability, substantial cooling should be performed.
Particularly, cooling of the drive motor such as a permanent magnet synchronous motor (PMSM) is very important for motor efficiency and protection of key components (for example, permanent magnet, coil, etc.). Cooling of the drive motor is major factor that determines performance and efficiency of the drive motor. In other words, the permanent magnet and the coil of the drive motor affect the performance of the motor according to temperature.
A scheme for cooling the drive motor includes an oil cooling scheme using oil and a water cooling scheme using water. For example, among them, in a cooling unit of a drive motor through the water cooling scheme, a coolant flow path is formed between an outer side of a stator and an inner side of a motor housing, and a coolant flows through the flow path so that heat generated by the stator may be cooled by the coolant.
Therefore, heat generated in the drive motor is transmitted to the motor housing through the stator core, and dissipated outside through the motor housing. Coolant flows in a coolant channel of the motor housing such that heat dissipation is maximized and the drive motor is cooled.
However, according to the conventional water cooling scheme, a cooling surface and heat dissipation of coolant with respect to the motor housing is limited, and it is very difficult to improve cooling performance of the drive motor.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.